Seismic exploration involves surveying subterranean geological media for hydrocarbon deposits. A survey typically involves deploying seismic sources and seismic sensors at predetermined locations. The sources generate seismic waves, which propagate into the geological medium creating pressure changes and vibrations. Variations in physical properties of the geological medium give rise to changes in certain properties of the seismic waves, such as their direction of propagation and other properties.
Portions of the seismic waves reach the seismic sensors. Some seismic sensors are sensitive to pressure changes (e.g., hydrophones), others to particle motion (e.g., geophones), and industrial surveys may deploy one type of sensor or both. In response to the detected seismic waves, the sensors generate corresponding electrical signals, known as traces, and record them in storage media as seismic data. Seismic data will include a plurality of “shots” (individual instances of the seismic source being activated), each of which are associated with a plurality of traces recorded at the plurality of sensors.
Seismic data is processed to create seismic images that can be interpreted to identify subsurface geologic features including hydrocarbon deposits. This imaging may involve propagation of wavefields through a velocity model of the subsurface, also called forward modeling. In complex subsurface areas, such as near and below salt bodies, seismic images often suffer uneven illumination or lack of illumination due to the sharp impedance contrast between salt and the surrounding sediments. Additionally, subsurface features such as steeply dipping top of salt and salt flanks may reflect seismic energy in a direction that is not directly recordable by the seismic sensors.
There exists a need for improved seismic images that will allow better seismic interpretation of geobodies that will, in turn, allow further improved imaging and interpretation of potential hydrocarbon reservoirs.